# Questions tagged [orbital-elements]

Orbital elements are a set of parameters that uniquely identify a specific orbit.

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### How do satellite trackers work when showing a "satellite"?

There are multiple sat trackers online where you can follow spacecraft orbiting Earth such as the ISS or the HST. I wonder how those trackers actually work when showing something near Earth, as the ...
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### Mean motion as indication for satellite (evasion) maneuvers

I am interested in detecting satellite maneuvers, e.g., to avoid collissions. As far as I understand the best publicly available data comes from TLEs although they have their own problems. What is the ...
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### Where does this formula for the argument of periapsis come from?

I was looking at Poliastro/Hapsira python code determining orbital elements from the position and velocity vector. On this line, argp or $\omega$ is determined as (...
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### Why my calculations for the eccentric anomalies at the start and end of an interplanetery transfer seem to be off?

For a game, to determine an interplanetary transfer I have implemented the method from here. Using the data for their example problem, I get the result with the lowest $\Delta v$ which appears ...
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### Is it possible to change a satellite's eccentricity without changing semimajor axis (instantaneous maneuver paradigm)? What else needs to "give"?

I've been wondering whether it's possible to change a satellite's eccentricity without changing its semi-major axis. (I'm assuming instantaneous changes in velocity.) At first I thought that this ...
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### How to calculate the ascending and descending node, as well as the true anomaly

I have the argument of perihelion, semi-major axis, eccentricity, inclination and mass. I have tried to look this up but get conflicting answers. Any help would be appreciated. (Edit) One physics ...
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### How to determine Euler parameters?

I have two questions and I can't solve the second one. Here it goes: Question 1 Consider a normalized system of units where µ = 1, Earth radius = 6378.165 km is the length unity, and T = 806.81 s is ...
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### Conversion of osculating orbital elements to TLE mean elements

I am looking for a method to resample TLE data, so they are regularly sampled. I wanted to use physical propagation to calculate elements at given time. However, the propagation of TLE by SGP4 returns ...
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### What's the orbital inclination range Crew Dragons can reach if the Falcon 9 first stage is about to be recovered?

Inspiration4 was one of the very few orbital spaceflights in this century that didn't go to a space station. Yet, it reached an orbital inclination of 51.6°, same as the ISS. I believe this is due to ...
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1 vote
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### Is my code correct to get six Keplerian parameters?

Is my code correct to get six Keplerian parameters? ...
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### What is the current state of the art in converting between mean and osculating orbital elements?

I want to implement algorithms to convert from mean to osculating elements, and vice versa. I've been digging through Vallado's text (fourth edition), and under ...
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### Converting Keplerian Orbital Elements into 2D State Vectors in Unity C#

I have done an extensive amount of research into this topic, but am really struggling to implement the math necessary to pull this off correctly. Just for some context: I'm trying to create a semi-...
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### Gibbs' method and position vectors' reference frame

As mentioned on this website https://www.studeersnel.nl/nl/document/technische-universiteit-delft/flight-orbital-mechanics-and-propulsion/chapter-05-preliminary-orbit-determination/4604099, we need to ...
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### In MATLAB, Computing a new TLE/orbit following a delta-v impulse?

I have already worked on this project for a week, and I still can not solve this problem by myself. How can I update data for the SGP4 OrbitPropagator in Matlab's ...
1 vote
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### Perifocal to ECI using Argument of Latitude

Suppose a satellite is orbiting Earth in a circular orbit. I know the following orbital elements: Inclination i, RAAN (Ω), Semi-major axis a (or orbit radius given that it is a circular orbit) ...
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### Calculate velocity vector of elliptical orbit given the position vector at that point, the instantaneous speed, the true anomaly, and the inclination?

Sorry if this is obvious, but I am an amateur at orbital mechanics and trigonometry was never my strong suit. I would like to calculate the velocity vector at a point in an orbit given: position ...
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### (In ECI) How can I compute the RAAN of an orbit given the eccentricity vector, the declination of the orbiter at apoapsis, and the inclination?

I am working on a personal project, and I want to write a program to obtain the RAAN given the angle of the eccentricity vector to the X-axis (ECI) along the XY plane, the declination (angle from XY ...
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### Orbit prediction for satellites using the Kepler model

I would like to know how to model the motion of satellites in orbit using Keplerian, i.e. develop a simulation model that tracks paths of satellites using Keplerian orbits in Python?
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### PseudoTLE creation

I am developing a script in python to obtain pseudo TLEs of a satellite, starting from its state vector. I have always used TLEs to propagate the satellite and predict its next pass over a ground ...
1 vote
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### Distance between a satellite and an orbit

I would like to compute the distance between a satellite and a specified orbit. For instance, for an orbit at 897 km altitude, 0 degree eccentricity, 99 degree inclination, and RAAN of 0 degrees on ...
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### How to use David Vallado's AstroLib to do reference frame conversions

Given a Keplerian Orbit description such as that in here: ...
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### Why does Earth's North Pole RA flip by ~180 deg around AD2000 relative to SSB? (JPL Horizons data)

Using JPL's Horizons API I see that the Earth's North Pole RA flipped by ~180 degrees quite suddenly around AD 2000. It was pretty stable around 180deg for at least 1000 years prior, and then remains ...
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### How would one obtain the longitude of satellite at the apogee?

I know that apogee longitude is a design point in Molniya orbits. Given the classical orbital elements, how can I find this value?
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### Where to get data for axis of rotation of solar system bodies?

Where can I get data for the axis of rotation of the (major) bodies of the solar system? For each solar system body, I want to get a unit vector of its axis of rotation (at a specified point in time). ...
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### Why is there a 38.6 km Earth-Moon distance difference between Ephemeris types "Observer table" and "Vector table" on Horizons Web Application?

The image above is a screenshot from Horizons Web Application with the Ephemeris type: Observer Table. It shows the distance (delta) from the geocentric observer location to target Moon on April 15, ...
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### Osculating conic orbital elements: Comparing SPICE's oscelt to MATLAB's ijk2keplerian functions

I have been using the SPICE Toolbox and wanted to derive orbital elements from a state vector $X$ in ECEF coordinates [1] in order to define a circular orbit around Earth. To do so I need first ...
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### How to find the SMA starting from a given repetition factor?

I need a help for an orbit design problem. My constraint is that the height is 480 km, the repetition factor has to be Q = 245/16 and the orbit must be sun-synchronous. I would like to find the SMA ...
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### I'm building a CubeSat for a short 8-day mission in LEO followed by a fairly quick reentry, what range of orbits to consider?

The goal of this CubeSat mission is to demonstrate CubeSat construction, operation, and communication in Low Earth orbit for 8 days or longer. Why the short mission time? Because the mission lacks ...
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### Vernal equinox direction and origin of longitude difference?

I am trying to visualise satellite orbits from a top-down perspective on the Earth, with down as 0° longitude. I am getting confused as to which the reference direction is using the right ascension of ...
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### Major axis larger than total of apogee and perigee?

I am trying to calculate the apogee and perigee using the orbital elements. I am checking my results against CALSPHERE 1 (https://www.n2yo.com/satellite/?s=900). I am getting 7363599.5m as the semi ...
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### Can you identify this space travel related equation?

Does anyone recognize the equation carved on this object? The only hint I have is that the back side has the word "orbit" carved into it. It may be incomplete or incorrectly copied. My best ...
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### Finding the largest X/Y/Z component of an orbit (in terms of ECI) using orbital elements?

If I wanted to find the largest component of an orbit on a single axis, like finding where on the orbit a satellite would reach its highest X component (not specifically an apoapsis, just when the X ...
1 vote
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### What type of galactic orbit will the Voyager probes have?

I know that they will eventually get close (within 10,000 light years) of our solar system, but will the orbit be circular or elliptical, around how much eccentricity, what would be a reasonable ...
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### Compute orbital parameters from transverse and radial velocity at a given distance from the focus

I've been pulling my hair on this problem for a couple of days now, researched a lot but have not been able to find results. Basically I'm writing a program capable of drawing a transfer orbit between ...